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34 * From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD$");
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/callout.h>
43 #include <sys/condvar.h>
44 #include <sys/kernel.h>
47 #include <sys/mutex.h>
49 #include <sys/sysctl.h>
52 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
53 "Average number of items examined per softclock call. Units = 1/1000");
54 static int avg_gcalls;
55 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
56 "Average number of Giant callouts made per softclock call. Units = 1/1000");
57 static int avg_mtxcalls;
58 SYSCTL_INT(_debug, OID_AUTO, to_avg_mtxcalls, CTLFLAG_RD, &avg_mtxcalls, 0,
59 "Average number of mtx callouts made per softclock call. Units = 1/1000");
60 static int avg_mpcalls;
61 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
62 "Average number of MP callouts made per softclock call. Units = 1/1000");
65 * allocate more timeout table slots when table overflows.
68 /* Exported to machdep.c and/or kern_clock.c. */
69 struct callout *callout;
70 struct callout_list callfree;
71 int callwheelsize, callwheelbits, callwheelmask;
72 struct callout_tailq *callwheel;
73 int softticks; /* Like ticks, but for softclock(). */
74 struct mtx callout_lock;
76 static struct callout *nextsoftcheck; /* Next callout to be checked. */
79 * Locked by callout_lock:
80 * curr_callout - If a callout is in progress, it is curr_callout.
81 * If curr_callout is non-NULL, threads waiting on
82 * callout_wait will be woken up as soon as the
83 * relevant callout completes.
84 * curr_cancelled - Changing to 1 with both callout_lock and c_mtx held
85 * guarantees that the current callout will not run.
86 * The softclock() function sets this to 0 before it
87 * drops callout_lock to acquire c_mtx, and it calls
88 * the handler only if curr_cancelled still 0 when
89 * c_mtx is successfully acquired.
90 * wakeup_ctr - Incremented every time a thread wants to wait
91 * for a callout to complete. Modified only when
92 * curr_callout is non-NULL.
93 * wakeup_needed - If a thread is waiting on callout_wait, then
94 * wakeup_needed is nonzero. Increased only when
95 * cutt_callout is non-NULL.
97 static struct callout *curr_callout;
98 static int curr_cancelled;
99 static int wakeup_ctr;
100 static int wakeup_needed;
103 * Locked by callout_wait_lock:
104 * callout_wait - If wakeup_needed is set, callout_wait will be
105 * triggered after the current callout finishes.
106 * wakeup_done_ctr - Set to the current value of wakeup_ctr after
107 * callout_wait is triggered.
109 static struct mtx callout_wait_lock;
110 static struct cv callout_wait;
111 static int wakeup_done_ctr;
114 * kern_timeout_callwheel_alloc() - kernel low level callwheel initialization
116 * This code is called very early in the kernel initialization sequence,
117 * and may be called more then once.
120 kern_timeout_callwheel_alloc(caddr_t v)
123 * Calculate callout wheel size
125 for (callwheelsize = 1, callwheelbits = 0;
126 callwheelsize < ncallout;
127 callwheelsize <<= 1, ++callwheelbits)
129 callwheelmask = callwheelsize - 1;
131 callout = (struct callout *)v;
132 v = (caddr_t)(callout + ncallout);
133 callwheel = (struct callout_tailq *)v;
134 v = (caddr_t)(callwheel + callwheelsize);
139 * kern_timeout_callwheel_init() - initialize previously reserved callwheel
142 * This code is called just once, after the space reserved for the
143 * callout wheel has been finalized.
146 kern_timeout_callwheel_init(void)
150 SLIST_INIT(&callfree);
151 for (i = 0; i < ncallout; i++) {
152 callout_init(&callout[i], 0);
153 callout[i].c_flags = CALLOUT_LOCAL_ALLOC;
154 SLIST_INSERT_HEAD(&callfree, &callout[i], c_links.sle);
156 for (i = 0; i < callwheelsize; i++) {
157 TAILQ_INIT(&callwheel[i]);
159 mtx_init(&callout_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
160 mtx_init(&callout_wait_lock, "callout_wait_lock", NULL, MTX_DEF);
161 cv_init(&callout_wait, "callout_wait");
165 * The callout mechanism is based on the work of Adam M. Costello and
166 * George Varghese, published in a technical report entitled "Redesigning
167 * the BSD Callout and Timer Facilities" and modified slightly for inclusion
168 * in FreeBSD by Justin T. Gibbs. The original work on the data structures
169 * used in this implementation was published by G. Varghese and T. Lauck in
170 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
171 * the Efficient Implementation of a Timer Facility" in the Proceedings of
172 * the 11th ACM Annual Symposium on Operating Systems Principles,
173 * Austin, Texas Nov 1987.
177 * Software (low priority) clock interrupt.
178 * Run periodic events from timeout queue.
181 softclock(void *dummy)
184 struct callout_tailq *bucket;
186 int steps; /* #steps since we last allowed interrupts */
193 struct bintime bt1, bt2;
195 static uint64_t maxdt = 36893488147419102LL; /* 2 msec */
196 static timeout_t *lastfunc;
199 #ifndef MAX_SOFTCLOCK_STEPS
200 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
201 #endif /* MAX_SOFTCLOCK_STEPS */
208 mtx_lock_spin(&callout_lock);
209 while (softticks != ticks) {
212 * softticks may be modified by hard clock, so cache
213 * it while we work on a given bucket.
215 curticks = softticks;
216 bucket = &callwheel[curticks & callwheelmask];
217 c = TAILQ_FIRST(bucket);
220 if (c->c_time != curticks) {
221 c = TAILQ_NEXT(c, c_links.tqe);
223 if (steps >= MAX_SOFTCLOCK_STEPS) {
225 /* Give interrupts a chance. */
226 mtx_unlock_spin(&callout_lock);
228 mtx_lock_spin(&callout_lock);
233 void (*c_func)(void *);
238 nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
239 TAILQ_REMOVE(bucket, c, c_links.tqe);
243 c_flags = c->c_flags;
244 if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
246 c->c_flags = CALLOUT_LOCAL_ALLOC;
247 SLIST_INSERT_HEAD(&callfree, c,
252 (c->c_flags & ~CALLOUT_PENDING);
256 mtx_unlock_spin(&callout_lock);
260 * The callout may have been cancelled
261 * while we switched locks.
263 if (curr_cancelled) {
265 mtx_lock_spin(&callout_lock);
268 /* The callout cannot be stopped now. */
271 if (c_mtx == &Giant) {
273 CTR1(KTR_CALLOUT, "callout %p",
283 CTR1(KTR_CALLOUT, "callout mpsafe %p",
289 THREAD_NO_SLEEPING();
291 THREAD_SLEEPING_OK();
294 bintime_sub(&bt2, &bt1);
295 if (bt2.frac > maxdt) {
296 if (lastfunc != c_func ||
297 bt2.frac > maxdt * 2) {
298 bintime2timespec(&bt2, &ts2);
300 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
302 (intmax_t)ts2.tv_sec,
309 if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
311 mtx_lock_spin(&callout_lock);
316 * There might be someone waiting
317 * for the callout to complete.
319 wakeup_cookie = wakeup_ctr;
320 mtx_unlock_spin(&callout_lock);
321 mtx_lock(&callout_wait_lock);
322 cv_broadcast(&callout_wait);
323 wakeup_done_ctr = wakeup_cookie;
324 mtx_unlock(&callout_wait_lock);
325 mtx_lock_spin(&callout_lock);
333 avg_depth += (depth * 1000 - avg_depth) >> 8;
334 avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
335 avg_mtxcalls += (mtxcalls * 1000 - avg_mtxcalls) >> 8;
336 avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
337 nextsoftcheck = NULL;
338 mtx_unlock_spin(&callout_lock);
343 * Execute a function after a specified length of time.
346 * Cancel previous timeout function call.
348 * callout_handle_init --
349 * Initialize a handle so that using it with untimeout is benign.
351 * See AT&T BCI Driver Reference Manual for specification. This
352 * implementation differs from that one in that although an
353 * identification value is returned from timeout, the original
354 * arguments to timeout as well as the identifier are used to
355 * identify entries for untimeout.
357 struct callout_handle
358 timeout(ftn, arg, to_ticks)
364 struct callout_handle handle;
366 mtx_lock_spin(&callout_lock);
368 /* Fill in the next free callout structure. */
369 new = SLIST_FIRST(&callfree);
371 /* XXX Attempt to malloc first */
372 panic("timeout table full");
373 SLIST_REMOVE_HEAD(&callfree, c_links.sle);
375 callout_reset(new, to_ticks, ftn, arg);
377 handle.callout = new;
378 mtx_unlock_spin(&callout_lock);
383 untimeout(ftn, arg, handle)
386 struct callout_handle handle;
390 * Check for a handle that was initialized
391 * by callout_handle_init, but never used
392 * for a real timeout.
394 if (handle.callout == NULL)
397 mtx_lock_spin(&callout_lock);
398 if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
399 callout_stop(handle.callout);
400 mtx_unlock_spin(&callout_lock);
404 callout_handle_init(struct callout_handle *handle)
406 handle->callout = NULL;
410 * New interface; clients allocate their own callout structures.
412 * callout_reset() - establish or change a timeout
413 * callout_stop() - disestablish a timeout
414 * callout_init() - initialize a callout structure so that it can
415 * safely be passed to callout_reset() and callout_stop()
417 * <sys/callout.h> defines three convenience macros:
419 * callout_active() - returns truth if callout has not been stopped,
420 * drained, or deactivated since the last time the callout was
422 * callout_pending() - returns truth if callout is still waiting for timeout
423 * callout_deactivate() - marks the callout as having been serviced
426 callout_reset(c, to_ticks, ftn, arg)
434 #ifdef notyet /* Some callers of timeout() do not hold Giant. */
435 if (c->c_mtx != NULL)
436 mtx_assert(c->c_mtx, MA_OWNED);
439 mtx_lock_spin(&callout_lock);
440 if (c == curr_callout) {
442 * We're being asked to reschedule a callout which is
443 * currently in progress. If there is a mutex then we
444 * can cancel the callout if it has not really started.
446 if (c->c_mtx != NULL && !curr_cancelled)
447 cancelled = curr_cancelled = 1;
450 * Someone has called callout_drain to kill this
451 * callout. Don't reschedule.
453 mtx_unlock_spin(&callout_lock);
457 if (c->c_flags & CALLOUT_PENDING) {
458 if (nextsoftcheck == c) {
459 nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
461 TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c,
467 * Part of the normal "stop a pending callout" process
468 * is to clear the CALLOUT_ACTIVE and CALLOUT_PENDING
469 * flags. We're not going to bother doing that here,
470 * because we're going to be setting those flags ten lines
471 * after this point, and we're holding callout_lock
472 * between now and then.
477 * We could unlock callout_lock here and lock it again before the
478 * TAILQ_INSERT_TAIL, but there's no point since doing this setup
479 * doesn't take much time.
485 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
487 c->c_time = ticks + to_ticks;
488 TAILQ_INSERT_TAIL(&callwheel[c->c_time & callwheelmask],
490 mtx_unlock_spin(&callout_lock);
496 _callout_stop_safe(c, safe)
500 int use_mtx, wakeup_cookie;
502 if (!safe && c->c_mtx != NULL) {
503 #ifdef notyet /* Some callers do not hold Giant for Giant-locked callouts. */
504 mtx_assert(c->c_mtx, MA_OWNED);
507 use_mtx = mtx_owned(c->c_mtx);
513 mtx_lock_spin(&callout_lock);
515 * Don't attempt to delete a callout that's not on the queue.
517 if (!(c->c_flags & CALLOUT_PENDING)) {
518 c->c_flags &= ~CALLOUT_ACTIVE;
519 if (c != curr_callout) {
520 mtx_unlock_spin(&callout_lock);
524 /* We need to wait until the callout is finished. */
526 wakeup_cookie = wakeup_ctr++;
527 mtx_unlock_spin(&callout_lock);
528 mtx_lock(&callout_wait_lock);
531 * Check to make sure that softclock() didn't
532 * do the wakeup in between our dropping
533 * callout_lock and picking up callout_wait_lock
535 if (wakeup_cookie - wakeup_done_ctr > 0)
536 cv_wait(&callout_wait, &callout_wait_lock);
538 mtx_unlock(&callout_wait_lock);
539 } else if (use_mtx && !curr_cancelled) {
540 /* We can stop the callout before it runs. */
542 mtx_unlock_spin(&callout_lock);
545 mtx_unlock_spin(&callout_lock);
548 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
550 if (nextsoftcheck == c) {
551 nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
553 TAILQ_REMOVE(&callwheel[c->c_time & callwheelmask], c, c_links.tqe);
555 if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
557 SLIST_INSERT_HEAD(&callfree, c, c_links.sle);
559 mtx_unlock_spin(&callout_lock);
564 callout_init(c, mpsafe)
571 c->c_flags = CALLOUT_RETURNUNLOCKED;
579 callout_init_mtx(c, mtx, flags)
586 KASSERT((flags & ~CALLOUT_RETURNUNLOCKED) == 0,
587 ("callout_init_mtx: bad flags %d", flags));
588 /* CALLOUT_RETURNUNLOCKED makes no sense without a mutex. */
589 KASSERT(mtx != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
590 ("callout_init_mtx: CALLOUT_RETURNUNLOCKED with no mutex"));
591 c->c_flags = flags & CALLOUT_RETURNUNLOCKED;
594 #ifdef APM_FIXUP_CALLTODO
596 * Adjust the kernel calltodo timeout list. This routine is used after
597 * an APM resume to recalculate the calltodo timer list values with the
598 * number of hz's we have been sleeping. The next hardclock() will detect
599 * that there are fired timers and run softclock() to execute them.
601 * Please note, I have not done an exhaustive analysis of what code this
602 * might break. I am motivated to have my select()'s and alarm()'s that
603 * have expired during suspend firing upon resume so that the applications
604 * which set the timer can do the maintanence the timer was for as close
605 * as possible to the originally intended time. Testing this code for a
606 * week showed that resuming from a suspend resulted in 22 to 25 timers
607 * firing, which seemed independant on whether the suspend was 2 hours or
608 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
611 adjust_timeout_calltodo(time_change)
612 struct timeval *time_change;
614 register struct callout *p;
615 unsigned long delta_ticks;
618 * How many ticks were we asleep?
619 * (stolen from tvtohz()).
622 /* Don't do anything */
623 if (time_change->tv_sec < 0)
625 else if (time_change->tv_sec <= LONG_MAX / 1000000)
626 delta_ticks = (time_change->tv_sec * 1000000 +
627 time_change->tv_usec + (tick - 1)) / tick + 1;
628 else if (time_change->tv_sec <= LONG_MAX / hz)
629 delta_ticks = time_change->tv_sec * hz +
630 (time_change->tv_usec + (tick - 1)) / tick + 1;
632 delta_ticks = LONG_MAX;
634 if (delta_ticks > INT_MAX)
635 delta_ticks = INT_MAX;
638 * Now rip through the timer calltodo list looking for timers
642 /* don't collide with softclock() */
643 mtx_lock_spin(&callout_lock);
644 for (p = calltodo.c_next; p != NULL; p = p->c_next) {
645 p->c_time -= delta_ticks;
647 /* Break if the timer had more time on it than delta_ticks */
651 /* take back the ticks the timer didn't use (p->c_time <= 0) */
652 delta_ticks = -p->c_time;
654 mtx_unlock_spin(&callout_lock);
658 #endif /* APM_FIXUP_CALLTODO */